There are several known devices for simulating the sound of a heartbeat. None of these devices, however, has proven to be entirely successful for this purpose. For example, U.S. Pat. No. 3,888,233, issued to Ware, shows a dynamic loudspeaker driven by an oscillator producing periodic pulses. Unless adequate acoustical muffling or pulse-shaping circuitry is provided, the sound produced will be strident and tinny in character and will not resemble the distinctive low-frequency thumping sound of an actual heartbeat. Further, the fragility and limited excursion of a typical loudspeaker tends to result in an audible but not palpable heartbeat.
Another patent, U.S. Pat. No. 3,119,200, issued to Curtin et al, discloses an assembly having a diaphragm and a moving coil that is specially designed to simulate a heartbeat. While such an assembly may be more suitable than an ordinary loudspeaker, the complicated valving and switching arrangement militates against successful commercial exploitation.